Radiant cooling is a technical solution that has gained relevance in high-performance buildings due to its ability to reduce sensitive loads, improve thermal comfort, contribute to better indoor air quality and optimize energy consumption.
By: Ernesto Porras *
Unlike conventional systems that cool the air, these systems work by cooling surfaces – such as floors, ceilings or panels – that transfer heat by radiation, directly affecting the average radiant temperature of the space.
According to the ASHRAE Handbook – Applications and HVAC manufacturers, radiant systems allow you to operate with water at higher temperatures, reduce the use of fans, and minimize thermal stratification, all with lower energy consumption and without compromising comfort. These features allow it to be integrated with passive design strategies and approaches aimed at reducing energy consumption.
This article presents the essential technical principles of radiant cooling and shows two real applications in Colombia designed by our engineering and architecture team at Consultoría y Diseño en Climatización (CDC): an active cold beam system in a university building oriented to software development and a radiant floor system in a hospital tower intended for physiotherapy and fitness activities. Both cases illustrate how this technology can be effectively implemented in hot climates when thermal load, humidity, and space occupancy conditions are properly considered.
Technical Fundamentals of Radiant Cooling
Radiant cooling systems operate from the transfer of heat between cold surfaces and objects or people in space using thermal radiation. Unlike traditional HVAC systems, which rely on cooling and air movement, these systems act directly on the average radiant temperature (RMT), reducing the sensitive load without requiring large air flows.
The physical principle is clear: heat is transferred from warmer bodies (occupants, furniture, exposed surfaces) to cooler surfaces (floor, ceiling, or radiant panel), without requiring direct contact or a medium such as moving air for the exchange to occur. This heat transfer mechanism accounts for up to 50% of the heat balance between the human body and its indoor environment, so modifying the radiant temperature has a direct impact on thermal comfort.
An additional advantage of radiant systems is that, as they do not use air as the main means of thermal transport, they allow you to work with significantly lower air flows. This translates into smaller ducts, which is beneficial in projects where clearances in false ceilings are limited. This feature facilitates coordination with other networks and reduces the architectural impact of HVAC systems.
Main typologies
Radiant cooling systems can be classified according to the location of the emitting surface:
Radiant floor: system with pipes embedded in the slab or under the final finish, characterized by its high thermal inertia and uniform distribution of cooling
Ceiling or wall radiant panels: prefabricated systems with low thermal diffusivity and fast response that cool by direct radiation from the ceiling or wall. They are used in offices, classrooms or hospital environments where the aim is to maintain stable temperatures without generating annoying drafts. They should always be supplemented with complementary ventilation and dehumidification systems.
Active Chilled Beams: Ceiling-mounted units that combine induced convection cooling with a radiation transfer fraction
Operating conditions
Radiant systems typically operate with supply water between 14 and 18°C, which improves the performance of chillers by avoiding the need for temperatures as low as in typical HVAC systems. In addition, by reducing the use and size of fans, they reduce the electrical consumption associated with air movement.
A key consideration is that radiant cooling systems do not handle latent load, so they should always be supplemented with a dehumidification strategy, such as a DOAS system or stand-alone air handling units (AHUs). This condition is especially relevant in hot and humid climates, where improper design could generate condensation on cold surfaces.
Effects on comfort and thermal distribution
Radiant cooling tends to generate a more stable thermal environment, with no perceptible drafts and less vertical thermal stratification. This improves the feeling of comfort, especially in highly sensitive areas such as hospitals, offices or educational spaces. Controlling the TMR instead of the air temperature allows for thermal comfort with higher air temperatures, which supports the overall energy efficiency of the system.
Real applications in buildings in hot weather
Implementing radiant cooling systems in hot climates demands careful design that takes into account thermal load, humidity control, occupancy, and space usage conditions. At Consultoría y Diseño en Climatización (CDC), we have developed applied solutions that demonstrate the viability of this technology in real projects, maintaining high standards of comfort and efficiency. Below are two cases designed by our engineering and architecture team in Colombia that illustrate how this technology can be effectively integrated into high-performance buildings, even in demanding climatic contexts.
Case 1: Active Chilled Beams in University Building
In an academic building for the development of software and digital content, an air conditioning system based on active cold beams was designed for classrooms and collaborative spaces. One of the main constraints of the project was the limited height available between the slab and the false ceiling, which made it difficult to install large ducts required by a traditional all-air system.
As a solution, the CDC team developed a design with ceiling-mounted active chilled beams, fed with water at 15°C, which allow the sensitive load to be handled by radiation and induced convection, reducing the required airflow. The outdoor air supply was solved by independent treatment units (AHU) per floor, which ensure compliance with the ventilation rates established in ASHRAE 62.1 and control humidity. These AHUs drive primary air through vertical buitrons, allowing for efficient distribution without compromising the interior architecture.
The project was a finalist in the "Best HVAC Project" category of the 2025 Refriaméricas CALA Awards. This case demonstrates how active chilled beams can be an effective option for integrating thermal comfort, energy efficiency, and architectural compatibility in high-performance buildings located in hot climates such as Cali.
Case 2: Radiant floor in hospital tower
For a physiotherapy and fitness area within a hospital tower, a hydronic radiant floor system was designed as part of a comprehensive HVAC strategy. The system proposes the use of pipes embedded in the floor, fed by water at 15°C from the return of the central chiller system, with the aim of achieving uniform and continuous cooling. This condition is especially appropriate for spaces of prolonged use where stable comfort favors therapeutic processes.
The design also incorporates natural cross ventilation, through opposite windows, and a solar fireplace located on the roof, which acts as a passive hot air extractor. This integration reduces the use of forced air, minimizes thermal stratification and maintains comfortable conditions with low energy consumption.
This project aspires to LEED certification, so all the strategies were proposed under criteria of efficiency, comfort and sustainability. Part of this case was presented at the Building Automation Conference also at Refriaméricas 2025, as an example of integration between automation, bioclimatic architecture and radiant systems in hot climates. The case demonstrates that radiant cooling can be a technically viable solution in hot climates, provided that it is properly articulated with passive ventilation measures and the existing infrastructure of the central HVAC system is used.
Conclusions recommendations
Radiant cooling systems represent a technically viable solution for high-performance buildings in hot climates, provided they are properly integrated with other passive design, humidity control, and ventilation strategies. The experience in the two cases presented shows that their implementation is not only possible, but beneficial in terms of comfort, energy efficiency and architectural compatibility.
Based on the technical literature, the following points summarize the keys to its correct application in contexts of high temperature and humidity:
- Independent humidity control: It is essential to integrate dehumidification systems (such as DOAS or dedicated AHUs) to prevent condensation and maintain indoor air quality.
- Passive design compatibility: Radiant systems are enhanced when combined with strategies such as natural ventilation, solar control, and the use of thermal chimneys, as evidenced in the case of the hospital radiant floor.
- Thermal design adapted to the occupancy: In spaces of prolonged use such as classrooms or recovery areas, the thermal stability of radiant systems improves the perception of comfort by minimizing fluctuations and annoying drafts.
- Efficient use of the chilled water system: Working with return water at moderate temperatures (14–18 °C) improves chiller performance and reduces electricity consumption without affecting cooling capacity.
- Architectural and technical coordination: The reduction in duct size and airflow facilitates integration into projects with height restrictions or with particular architectural requirements.
The potential of radiant cooling in hot climates lies not only in the technology, but in its proper integration within a holistic approach to design. At CDC we will continue to bet on solutions that combine technical innovation, energy efficiency and a better quality of life for occupants.
Ernesto Porras – Consultant in Air Conditioning and Bioclimatic
Mechanical Engineer and Master in Bioclimatic Architecture and Urbanism, senior consultant with more than 17 years of experience in design, commissioning and evaluation of HVAC systems. Founder and director of Consultoría y Diseño en Climatización S.A.S. (CDC), he has participated in strategic projects such as Thermal Districts Colombia Phase II for UNIDO and the National Roadmap for Net Zero Carbon Buildings, promoting the transition to more efficient and resilient buildings. In addition, he is an international lecturer and trainer in air conditioning and sustainable construction with the purpose of transforming the industry and promoting environments that optimize the quality of life of its occupants.
Contact: [email protected]
